Quest

Not familiar with iView boxes but should be similar to most others.

No, you don't need to change the setting from Astra UK.

If QuestHD is on a frequency not listed on the iView box, you will need to add it.

Quest HD (and Food Network, DMAX, etc) frequency:
DVB-S2
12382
Horizontal
SR: 29500
FEC: 2/3

Or if you're doing a rescan, there should be an option like Network Scan that you could enable which would update the frequency list that the box scans for channels.

Also, on some boxes, they won't add a channel if it already exists so may be no harm to delete the listed dead channels first.